Fig. 16

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Illustrations of the evolution of the pore scale fluid distribution. During pressure depletion experiments, at some point gas bubbles are nucleated which initially may grow, but ripening will on the long run cause smaller bubbles to disappear and larger bubbles grow until individual pores are completely filled. Both for grow and ripening, pore throats act as natural barriers [49]. Upon injection of gas at or near the bubble point, gas diffuses ahead of the “convective front”. That changes the local composition such that the bubble point decreases below the local conditions. That leads to a phase separation into liquid and gas. The gas then locates in the center of pores while the liquid (that preferentially wets the solid) locates in the pore throats. In this way gas advances, i.e. is mobile, without having a permanent connectivity. That distribution will then undergo similar ripening processes as in the pressure depletion case.